NERVOUS SYSTEM AND SENSE ORGANS OF AMIURUS. 453 
PLATE VI. 
BO.—Basi-occipital. 
C. I.—Centrum of Ist vertebra. 
D M.—Dorsal musculature. 
# O.—Exoccipital. 
L. tri.—Trigeminal lobes. 
LL. vag.—Vagus lobes. 
N. VIII. post.—Posterior division of auditory nerve. 
R. ac. vag. I —Acustic root of vagus. 
R. lag.—Ramus lagene cochlee. 
R. lat. V.—Ramus lateralis trigemini. 
R. sac.—Ramus sacculi. 
T. A.—Tuberculum acusticum. 
Vag.—Vagus nerve. 
as, —Asteriscus. 
asi.—Atrium sinus imparis. 
cr.— Crest of basi-occipital between fovex sacculi. 
cl.—Claustrum. 
d+ ? *_[orsal roots of 1st, 2nd and 3rd spinal nerves. 
de.—Ductus endolymphaticus. 
dm.—Patch of dura mater on basi-occipital and upper surface of 
first vertebra. 
dus.—Wall of ductus utriculo-saccularis. 
fr.—Frontal semi-circular canal. 
fr, a.—Ampulla of semi-circular canal. 
fs.—Fovea sacculi. 
in.—-Ineus. 
lag.—Lagena cochlez. 
na I,—Neural arch of Ist vertebra. 
mall,—Malleus. 
s.—Sagitta. 
sac—Sacculus. 
sc.—Saccus endolymphaticus. 
sp.—Saccus paravertebralis, 
st. ant.—Anterior spoon-shaped process of stapes. 
st. art.—Articular process of stapes. 
st. asc.—Ascending process of stapes. 
st. t. Tendon attaching incus to stapes. 
u.—Utriculus, 
vi 2 8__Ventral roots Ist, 2nd and 8rd spinal nerves. 
Figs. 1-11 represent selected sections from a frontal series through the part 
surrounding the central nervous system of Amiwrus from the posterior face of 
the first vertebra as far forward as the suture between the ex-occipital and 
the prootics. Las 
Fig. 1.—The dorsal and ventral roots of the third spinal nerve piercing the 
membranous wall of the neural canal, which is lined by the dura 
mater vertebralis, while the spinal cord is closely invested by 
